Nasal masks which are intended to be used for delivering air under continuous positive pressure to sleeping persons ideally are required to exhibit seemingly incompatible characteristics. They should provide a complete peripheral seal around the region of contact with wearers' faces and, in order to do so, accommodate the vastly different facial features of different persons. They should be capable of maintaining the peripheral seal for prolonged periods of time, throughout the night for persons using the masks in the treatment of sleep apnea, and accommodate significant degrees of conscious and semi-conscious movement on the part of wearers. Finally, the masks should be sufficiently comfortable to enable wearers to enjoy natural sleep and, thus, should intrude as little as possible on the feeling of well being of a user.
A nasal mask which goes a long way toward meeting these requirements and which has received widespread approval from both medical advisers and users is disclosed in Australian Patent No. 643994, dated May 16, 1991, granted to The University of Sydney. This mask is radically different from prior art masks which rely on peripheral sealing, in that it incorporates a face contacting portion which is formed from an elastomeric material and which is shaped to define a balloon-like chamber. When gas is admitted to the chamber it tends to balloon outwardly and, when fitted to a wearer, the face contacting portion is caused to overlie a region of the wearer's face and seal three-dimensionally with the contours of the overlayed region.
For practical reasons, the above described mask is in use mounted to or integrated with a rigid shell-like moulding which does not (or need not) contact the wearer's face. The shell is provided to enable a gas supply line to be connected to the mask, to facilitate fastening of the mask to a user's face and to minimise the risk that movement of the gas supply line will disrupt the seal between the mask and the wearer's face. However, it has now been determined that, whilst the shell does provide a stabilising connection for the gas supply line, any force that is exerted on the shell by the gas supply line will tend to be transmitted to the mask itself, primarily because of the rigidness of the shell. Also, because the shell is interposed between the mask and the gas supply line, any lateral movement of the supply line will be amplified by an amount proportional to the distance between the mask sealing region and the point of connection with the supply line.
The present invention seeks to minimise these difficulties by providing a mask which avoids the need for a rigid shell-like moulding to be interposed between the mask itself and the gas supply line.